Metamaterials are artificial composite materials. A uniform metamaterial may be formed as a repeated unit cell structure, the unit cell dimensions typically being somewhat less than the operational wavelength. For example, the operating wavelength may be at least three times the unit cell parameter, and may be at least 5 times the unit cell parameter. The electromagnetic properties of the metamaterial, such as permittivity, permeability, and refractive index, can be calculated using an effective median theory.
An interesting aspect of metamaterials is that electromagnetic properties not available in naturally occurring materials can be obtained. In particular, negative index materials, for example having a negative refractive index, can be created.
For radar applications, a unit cell may comprise a metal foil pattern fabricated using conventional printed circuit board techniques. However, limitations on lithography restrict the use of such circuit board based approaches to longer wavelength applications, such as radar. Most previous applications of metamaterials have been radar applications.
However, there is a great need for improved optical components.